Many material handling implements include so-called "power takeoff" arrangements which permit the power source of the implement to drive an associated device, such as a rotary tiller, a wood splitter, or a like attachment. Such power takeoffs can comprise a mechanical power source, such as a driven shaft, or alternately can comprise a hydraulic valve arrangement for supplying pressurized fluid from the material handling implement to a hydraulic motor or the like on an associated attachment. Such arrangements are highly desirable for enhancing the versatility of material handling implements since they permit a wide variety of driven attachments to be operated by the source of power on the implement.
The preferred manner in which a hydraulic power takeoff valve is controlled in part depends upon the type of attachment to be operated. For example, when a rotary tiller is attached to a tractor with its power takeoff valve supplying pressurized fluid to the tiller's hydraulic motor, it is ordinarily preferable to provide a control arrangement which permits the hydraulic valve to be releasably maintained in an "on" position, thus freeing the hands of the operator for guiding the tractor. In contrast, a device such as a hydraulic wood splitter is usually operated by discrete periods of fluid pressurization, rather than continuous pressurization. Accordingly, efficient splitter operation requires a control arrangement for the tractor's power takeoff valve that is configured to permit selective fluid pressurization of the hydraulic actuator of the splitter, with the control arrangement permitting the valve to return to a centered, neutral position when the control handle is released.
In one previously known control arrangement, a control handle and a handle bracket are provided for selectively moving the spool of a hydraulic power takeoff valve. In this previous arrangement, the handle bracket includes a pair of spaced apart wall portions which are positioned on generally opposite sides of one end of the valve spool. The control handle pivots with respect to one of the wall portions as it is moved within a guide slot defined by the other wall portion. The handle is pivotally interconnected with the valve spool between the opposed wall portions of the bracket so that movement of the control handle reciprocably moves the valve spool.
The above-described previous control arrangement has typically been employed in association with a self-centering hydraulic valve. In order to permit the valve to be maintained at one end of its stroke against the action of its centering spring, a detent is provided adjacent the guide slot within which the handle is movable. By positioning the handle in the detent, the valve spool is maintained in a position such that a continuous supply of pressurized fluid is provided to an associated device, such as for continuous operation of a rotary tiller.
While this type of control arrangement desirably permits "hands off" operation of the power takeoff valve for continuous pressurized fluid supply, such an arrangement is not as well suited for use with a device such as a wood splitter since non-continuous fluid supply is usually desired. With the above control arrangement, inadvertent movement of the control handle into the detent can cause the supply of pressurized fluid to continue even though an associated hydraulic actuator (such as on the splitter) has moved through its full stroke. Additionally, the above control arrangement usually is configured to facilitate convenient operation from the control area of the associated tractor, with manipulation of the control arrangement from behind the tractor (such as for operation of a wood splitter) being somewhat less convenient.
In view of the foregoing, it is desirable to provide a control arrangement such as for operation of a self-centering, hydraulic power takeoff valve which in one mode of operation facilitates maintaining the valve in an "on" position, while in another mode of operation permitting the valve to self-center when the handle of the control arrangement is released.